scholarly journals Comparison of von Willebrand factor platelet‐binding activity assays: ELISA overreads type 2B with loss of HMW multimers

2020 ◽  
Vol 18 (10) ◽  
pp. 2513-2523
Author(s):  
Attila Szederjesi ◽  
Luciano Baronciani ◽  
Ulrich Budde ◽  
Giancarlo Castaman ◽  
Paola Colpani ◽  
...  
Keyword(s):  
Von Willebrand Factor ◽  
Binding Activity ◽  
Platelet Binding ◽  
Von Willebrand ◽  
Willebrand Factor

LOCALIZATION OF THE PLATELET-BINDING AND HEPARIN-BINDING DOMAINS OF BOVINE VON WILLEBRAND FACTOR

1987 ◽  
Author(s):  
Edward P Kirby ◽  
Mary Ann Mascelli ◽  
Carol Silverman ◽  
Daniel W Karl
Keyword(s):  
Von Willebrand Factor ◽  
Human Platelets ◽  
Binding Activity ◽  
Heparin Binding ◽  
Amino Groups ◽  
Binding Domains ◽  
Platelet Binding ◽  
Diamondback Rattlesnake ◽  
Von Willebrand ◽  
Willebrand Factor

Bovine von Willebrand Factor (vWF) binds directly to human platelets and also to heparin-agarose. Cleavage of vWF with Protease I, a metalloenzyme isolated from the venom of the western diamondback rattlesnake, produces two major fragments with apparent Mr of 250 kD and 200 kD. The 200 kD fragment competes with native vWF for binding to the GPIb-associated vWF receptor on formalin-fixed human platelets and has weak platelet-agglutinating activity. It is composed of three polypeptide chains of apparent Mr of 97 kD, 61 kD, and 35 kD. Monoclonal antibodies #2 and H-9, which inhibit binding of vWF to a GPIb-associated receptor of platelets, recognize the 200 kD fragment.Modification of vWF with ^5x-la.beled. Bolton-Hunter reagent (I*-BHR) causes inhibition of platelet-agglutinating activity at very low levels of incorporation. Modification of less than 2% of the amino groups in vWF causes 50% loss of platelet agglutinating activity and a decreased affinity of vWF for binding to platelets. Labeling with I*-BHR does not block binding to heparin-agarose, even when 5-10% of the amino groups are modified. Differential labeling at pH 7.0 and pH 8.5, followed by proteolytic fragmentation with Protease I, suggests that it is the modification of amino groups on the 200 kD fragment which is responsible fpr the decrease in platelet binding activity. Modification of the 97 kD peptide chain is best correlated with this loss of platelet binding activity.Heparin inhibits the agglutination of human platelets by bovine vWF. The 200 kD fragment of vWF binds both to platelets and to heparin-agarose. These observations suggest that the heparin-binding and platelet-binding domains of vWF, although distinct from one another, reside in the same region of the vWF molecule. The platelet-binding domain contains a small number of very reactive amino groups which are required for vWF binding to human platelets.These studies were supported by a grant from the National Institutes of Health (#HL27993).

scholarly journals In Vitro Assessment of von Willebrand Factor in Cryoprecipitate, Antihemophilic Factor/VWF Complex (Human), and Recombinant von Willebrand Factor

2019 ◽  
Vol 25 ◽  
pp. 107602961987397
Author(s):  
Meaghan E. Colling ◽  
Kenneth D. Friedman ◽  
Walter H. Dzik
Keyword(s):  
Von Willebrand Factor ◽  
Binding Activity ◽  
Von Willebrand Disease ◽  
Enzyme Linked Immunosorbent Assay ◽  
Major Bleeding Episode ◽  
Platelet Binding ◽  
Group A ◽  
Von Willebrand ◽  
Willebrand Factor

Patients with von Willebrand disease (VWD) often require treatment with supplemental von Willebrand factor (VWF) prior to procedures or to treat bleeding. Commercial VWF concentrates and more recently recombinant human VWF (rVWF) have replaced cryoprecipitate as the mainstay of therapy. In comparison with cryoprecipitate, the VWF content and multimer distribution under current manufacturing processes of these commercial products has not been reported. We measured the factor VIII (FVIII:C), VWF antigen (VWF:Ag), VWF collagen-binding activity (VWF:CB), VWF platelet-binding activity by GPIbM enzyme-linked immunosorbent assay (VWF:GPIbM), and percentage of high-molecular-weight (HMWM) VWF in 3 pools of group A and O cryoprecipitate, 3 vials of VWF concentrate (Humate-P), and 1 lot of rVWF (Vonvendi). We found that both group O and group A cryoprecipitate have significantly higher ratios of VWF:GPIbM activity and FVIII:C activity relative to VWF:Ag and have better preservation of HMWM than Humate-P. Although not compared statistically, rVWF appears to have more HMWM VWF and a higher ratio of VWF:GPIbM to VWF:Ag than Humate-P and cryoprecipitate. The estimated acquisition cost for our hospital for treating one major bleeding episode was more than 4-fold higher with Humate-P and 7- to 10-fold higher with rVWF than with cryoprecipitate.

scholarly journals Phage Display Functionally Defines Variants in the Von Willebrand Factor Platelet Binding Domain

Blood ◽  
2021 ◽  
Vol 138 (Supplement 1) ◽  
pp. 1033-1033
Author(s):  
Andrew Yee ◽  
Melda Arslantas Guzel ◽  
Manhong Dai ◽  
Fan Meng ◽  
David Ginsburg
Keyword(s):  
Phage Display ◽  
Von Willebrand Factor ◽  
Phage Display Library ◽  
Binding Activity ◽  
Binding Domain ◽  
Single Amino Acid ◽  
Missense Variants ◽  
Platelet Binding ◽  
Von Willebrand ◽  
Willebrand Factor

Abstract Missense variants in the von Willebrand factor (VWF) platelet binding domain, A1, may pathologically hyperactivate or weaken interactions with its platelet receptor, GPIbα, and lead to von Willebrand disease (VWD) subtypes 2B or 2M, respectively. Variants identified in VWD patients and tested as recombinant VWF have supported genotype-phenotype associations and subtyping of VWD by genetic analyses. However, novel variants, most classified as variants of uncertain significance (VUS) are poorly defined. To functionally characterize a large subset of VWF A1 variants (P1254-L1460), we screened a phage display library for binding to a recombinant form of GPIbα used to clinically assess VWF platelet binding activity, GPIbM. Comprised of ~5x10 6 independent clones, the phage display library contained 1,427 unique, missense variants (~36% of all possible single amino acid substitutions) which could be scored for significant enrichment, depletion, or no change following selection for GPIbM binding. The enrichment of phage displayed VWD variants previously classified as VWD subtype 2B significantly segregated from reported 2M variants (mean fold change from preselected phage ~1.06 for 2B vs. ~0.68 for 2M, p < 0.005). To further validate these findings, five depleted, four unchanged, and seven enriched VWF A1 variants were introduced into the full length VWF sequence by site-directed mutagenesis and expressed by transient transfection of HEK293T cells. Conditioned media were collected and analyzed for VWF level (VWF:Ag) and activity (VWF:GPIbM). Of the sixteen variants examined, fourteen (87.5%) exhibited a VWF GPIbM:Ag ratio that was concordant with the phage display findings. Furthermore, the VWF GPIbM:Ag ratios were well correlated with the degree of enrichment by phage display (Pearson R = 0.69, p< 0.01). Taken together, these findings demonstrate phage display as a high content approach to measure and functionally define the platelet-binding activity of genetic variants within the VWF A1 domain. Disclosures Ginsburg: Takeda: Patents & Royalties.

The Interaction of Botrocetin with Normal or Variant von Willebrand Factor (Types IIA and IIB) and Its Inhibition by Monoclonal Antibodies that Block Receptor Binding

1992 ◽  
Vol 68 (04) ◽  
pp. 464-469 ◽  
Author(s):  
Y Fujimura ◽  
S Miyata ◽  
S Nishida ◽  
S Miura ◽  
M Kaneda ◽  
...  
Keyword(s):  
Monoclonal Antibodies ◽  
Von Willebrand Factor ◽  
Binding Activity ◽  
Von Willebrand Disease ◽  
Platelet Glycoprotein ◽  
Normal Individuals ◽  
Rag 1 ◽  
The One ◽  
Von Willebrand ◽  
Willebrand Factor

SummaryWe have recently shown the existence of two distinct forms of botrocetin (one-chain and two-chain), and demonstrated that the two-chain species is approximately 30 times more active than the one-chain in promoting von Willebrand factor (vWF) binding to platelet glycoprotein (GP) Ib. The N-terminal sequence of two-chain botrocetin is highly homologous to sea-urchin Echinoidin and other Ca2+-dependent lectins (Fujimura et al., Biochemistry 1991; 30: 1957–64).Present data indicate that purified two-chain botrocetin binds to vWF from plasmas of patients with type IIA or IIB von Willebrand disease and its interaction is indistinguishable from that with vWF from normal individuals. However, an “activated complex” formed between botrocetin and IIB vWF expresses an enhanced biological activity for binding to GP Ib whereas the complex with IIA vWF has a decreased binding activity. Among several anti-vWF monoclonal antibodies (MoAbs) which inhibit ristocetin-induced platelet aggregation and/or vWF binding to GPIb, only two MoAbs (NMC-4 and RFF-VIII RAG:1) abolished direct binding between purified botrocetin and vWF. This suggests that they recognize an epitope(s) on the vWF molecule in close proximity to the botrocetin binding site.

Plasma Derived von Willebrand Factor Preparations: Collagen Binding and Ristocetin Cofactor Activities

1997 ◽  
Vol 78 (02) ◽  
pp. 930-933 ◽  
Author(s):  
Ping Chang ◽  
D L Aronson
Keyword(s):  
Von Willebrand Factor ◽  
Functional Activity ◽  
Binding Activity ◽  
Collagen Binding ◽  
Binding Function ◽  
Cofactor Activity ◽  
Von Willebrand ◽  
Willebrand Factor ◽  
Ristocetin Cofactor ◽  
Ristocetin Cofactor Activity

SummaryFive plasma preparations (11 lots) used in the treatment of von Willebrand’s disease (vWD) were evaluated. The collagen binding function of von Willebrand factor (vWF) containing preparations was compared with the ristocetin cofactor activity and the vWF antigen. Some preparations have higher ratio of functional activity (ristocetin cofactor and collagen binding) relative to the antigen than is found in normal plasma. The ristocetin cofactor activity and the collagen binding activity are tightly correlated (r = .95). Ultracentrifugal (UCF) analysis was used to compare the size distribution of vWf antigen, ristocetin cofactor and collagen binding activity. The sedimentation of all of the vWF parameters in the plasma products was slower than in plasma. In plasma products the ristocetin cofactor activity sediments the most rapidly, the collagen binding activity is slower and the antigen the slowest. The collagen/antigen ratio decreases with decreasing vWF size. Assignment of potency to vWF containing preparations utilizing the collagen binding activity may be more precise and as accurate as with the traditional ristocetin cofactor assay.

scholarly journals Acquired von Willebrand disease caused by an autoantibody selectively inhibiting the binding of von Willebrand factor to collagen

Blood ◽  
1994 ◽  
Vol 84 (10) ◽  
pp. 3378-3384 ◽  
Author(s):  
PJ van Genderen ◽  
T Vink ◽  
JJ Michiels ◽  
MB van 't Veer ◽  
JJ Sixma ◽  
...  
Keyword(s):  
Von Willebrand Factor ◽  
Binding Activity ◽  
Von Willebrand Disease ◽  
Low Grade ◽  
Bleeding Tendency ◽  
Glycoprotein Ib ◽  
Acquired Von Willebrand Disease ◽  
Recurrent Epistaxis ◽  
Von Willebrand ◽  
Willebrand Factor

Abstract An 82-year-old man with a low-grade malignant non-Hodgkin lymphoma and an IgG3 lambda monoclonal gammopathy presented a recently acquired bleeding tendency, characterized by recurrent epistaxis, easy bruising, and episodes of melena, requiring packed red blood cell transfusions. Coagulation studies showed a von Willebrand factor (vWF) defect (Ivy bleeding time, > 15 minutes; vWF antigen [vWF:Ag], 0.08 U/mL; ristocetin cofactor activity [vWF:RCoF], < 0.05 U/mL; collagen binding activity [vWF:CBA], 0.01 U/mL; absence of the high molecular weight multimers of vWF on multimeric analysis). Mixing experiments suggested the presence of an inhibitor directed against the vWF:CBA activity of vWF without significantly inhibiting the FVIII:C, vWF:Ag, and vWF:RCoF activities. The inhibitor was identified as an antibody of the IgM class by immunoabsorption of vWF and inhibitor-vWF complexes from the plasma of the patient. Subsequent immunoprecipitation experiments using recombinant fragments of vWF showed that the inhibitor reacted with both the glycoprotein Ib binding domain (amino acids [aa] 422–826) and the A3 (aa 909–1112) domain of vWF, but not with the A2 (aa 716–908) or D4 (aa 1183–1535) domains. We conclude that the IgM autoantibody inhibits the vWF:CBA activity by reacting with an epitope present on both the glycoprotein Ib and A3 domains of vWF.

scholarly journals von Willebrand factor released from Weibel-Palade bodies binds more avidly to extracellular matrix than that secreted constitutively

Blood ◽  
1987 ◽  
Vol 69 (5) ◽  
pp. 1531-1534 ◽  
Author(s):  
LA Sporn ◽  
VJ Marder ◽  
DD Wagner
Keyword(s):  
Extracellular Matrix ◽  
Endothelial Cells ◽  
Von Willebrand Factor ◽  
Immunofluorescent Staining ◽  
Cultured Endothelial Cells ◽  
Human Foreskin Fibroblasts ◽  
Platelet Binding ◽  
The Matrix ◽  
Von Willebrand ◽  
Willebrand Factor

Abstract Large multimers of von Willebrand factor (vWf) are released from the Weibel-Palade bodies of cultured endothelial cells following treatment with a secretagogue (Sporn et al, Cell 46:185, 1986). These multimers were shown by immunofluorescent staining to bind more extensively to the extracellular matrix of human foreskin fibroblasts than constitutively secreted vWf, which is composed predominantly of dimeric molecules. Increased binding of A23187-released vWf was not due to another component present in the releasate, since releasate from which vWf was adsorbed, when added together with constitutively secreted vWf, did not promote binding. When iodinated plasma vWf was overlaid onto the fibroblasts, the large forms bound preferentially to the matrix. These results indicated that the enhanced binding of the vWf released from the Weibel-Palade bodies was likely due to its large multimeric size. It appears that multivalency is an important component of vWf interaction with the extracellular matrix, just as has been shown for vWf interaction with platelets. The pool of vWf contained within the Weibel-Palade bodies, therefore, is not only especially suited for platelet binding, but also for interaction with the extracellular matrix.

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